Permanent magnet chuck



Oct. 24, 1944. J. T. BEECHLYN PERMANENT MAGNET CHUCK Filed Feb. 7, 19412 Sheets-Sheet l Oct. 24, 1944. J. 'r. BEECHLYN PERMANENT MAGNET CHUCK 2Shams-Shee 2 Filed Feb. 7, 1

Patented Oct. 24, 1944 John -'I. Beechlyn, Worcester, Mass., assignor to0. S. Walker 00. Inc., Worcester, Mass, a corporation of MassachusettsApplication February 7, 1941, Serial No. 377,854 (Cl. 175-367) 15Claims.

This invention relates in'general to permanent magnetic chucks and moreparticularly to such chucks oi the round or rotary type.

Objects of the invention include the provision of a simple andinexpensive permanent magnet rotary chuck adapted to be used in lathes,grinding machines, etcl, wherein the chuck will rotate on its axis tohold centered work; the provision of a rotary chuck in which a singleannular magnet is used to provide the work holding flux; the provisionof a rotary chuck in which an annular magnet is supported on a centralspindle and is provided with a magnetic valve rotatably mounted on thespindle for rendering the magnet effective for holding or releasing thework, the provision of a more rigid and stronger work holding plateobtained by coating the pole pieces at the gaps with soft tin, andutilizing a hardened tin alloy for filling the gaps, whereby thehardened tin will alloy with the soft tin to produce a uniform hard,strong gap construction; and the provision of a rotary permanent magnetchuck of new construction and improved holding power,

in which the chuck parts may be held together by the attractionof themagnet, the parts being applied to a tapered pin or arbor l which isadapted to be held in a head stock of a lathe, for example. Othersupports might easily be used, as a bolt for'use with slotted faceplates, or the tapered arbor could be omitted and the chuck used as aflat work holder; In any case, as illustrated, the arbor lfl is providedwith a straight cylindrical member I2 of iron and this member has areduced threaded or headed over member. l4 integral therewith for apurpose to be described. v

A circular, parallel-sided iron plate [8 having a central aperturefitting the cylindrical member I2 is positioned as shown inFig. 2adjacent the taper at Ill and remote from the member l4. This plate isbeveled on one edge as at I8 and has an annular recess at 20, and isadapted to closely engage member l2 at the aperture, having a turningfit therewith.

supported onga central spindle which acts as a return circuit for theflux.

Other objects and advantagesof the invention will appear hereinafter.

Reference is to be had to the accompanying drawings, in which Fig. l isa front view of one form of a chuck embodying the present invention, andshowing the work holding plate, with parts broken away to illustrate themagnetic valve ring to ;turn the flux on and oil as to work holdingeffect;

Fig. 21s a section taken on line 2--2 ofl ig. 1; Fig; 3 is a front viewof another form of the invention;

P18. 4 is a section on line 4-4 of Fig. 3; I Fig. 5 is a perspective andsectional view of the magnetic valve ring used in the form of theinvention shown in Fig. 4;

Fig. 8 is a central sectional view of a chuck according to the presentinvention adapted for automatic control;

Fig; is-a front view of another form of the invention with part insection as on line 1-1 of Fig. 8;

. Fig. 8 is a central sectional view through the device of Fig.7; and

Hg. 9 is a broken view similar to Fig. 8 but showing the parts in workrelease position.

Referring to Figs. 1 and 2, it will be seen that it has'been chosen toillustrate this invention as A two-part annular work holding plate 22 ismade up of an outer iron member 24 and an inner iron member 26. Thesemembers have complementary' tapered slots, interiorly of. member 24 andexteriorly or peripherally of member 26, so that tapered iron pieces 28,30, respectively, are produced, to interfit in continuous spacedrelation as clearly shown in Fig. l. The space is utilized as a gap andis filled with non-magnetic material 32, thus permanently holding theparts together. I. is to be particularly noted that this gap is paralleland concentric with member 12 at the innermost portions 34, see Fig. -2,but the outermost portions at 38 extend. at a considerable angle tomember I2, as also shown in Fig. 2, while still being concentric. Part26 is apertured and countersunk as at 28, ig. 2, to fit and-be securedto member l2 by the reduced member. l4. By

this means, plate 22 is secured concentrically to member l2, and part 24has a peripheral recess 40, while a central recess is provided for usein working hollow members or rings.

and conceals the magnet, and is interiorly re- A- non-magnetic brass orother sleeve 42 surrounds member l2 and besides providing a gap, thissleeve spaces plates l8 and 22, holding them apart An annular magnet 44of large section, and magnetized to have its poles on opposite 'fiatfaces 40, 48, respectively, is arranged about sleeve 42 and may beslightly spaced therefrom as well as from an iron fiat ring '50 havingcircular corners to. fit the recesses 20, 40, as shown. This ring spansthe space between plates l8 and '22,

cessed to provide a gap II which may be filled by a non-magneticmaterial. It will be seen that the etic section of ring II is very smallcompared to that of either member of the plate The remaining element ofthis construction is the valve comprising an annular iron piece 52having a flat surface adjacent pole face 48 of the magnet and extendingbetween sleeve 42 and flat ring 50. Flat lands 54 shaped to correspondto pieces 28, 38 rise from the other surface of the piece 52 and theselands are spaced corresponding distances, see Fig. 1. The tops of thelands are arranged to bear on the interior surfaces of the iron pieces28, 38, and are of a size to correspond to these interior surfaces.

In the operation of the device, the tapered arbormay be held in a headstock, so that the exterior flat face of the combined member 24. 28extends toward the tail stock, and forms the work holding surface. Ifthe iron piece 52 be turned on sleeve 42 to a position where the lands54 align with the iron pieces 28, flux from the magnet 44 will passthrough member 24 into a work piece on the chuck, and thus over gap 32at all points of the latter. The flux will then pass into member 28,thru I4, I2, I6 and complete the magnetic circuit to the magnet. If,however, the member 52. is turned relatively to plate 22 so that lands54 align with iron pieces 30, the flux will pass directly into member I4without traversing gap 32, so that any work piece on the holding platewill be released. It is to be especially noted that ring 58 comprises ameans for the relative turning of the parts, and this ring can besecured to plate 22, or to member 52 for the relative turning, so thateither the parts are constantly urged together in an axial directionunder influence of the magnet, so that the spacing efiect of sleeve 42becomes of some importance in leaving member 52 free to turn. Also, ifbolts are used in place of the tapered arbors, two or three chucks maybe secured to iii) a single slotted face plate so that large rings maybe held for light grinding operations.

The magnetic effect of'turning ring is to provide a constant path for asmall flux thru the work in a direction opposite to the direction ofgthe holding flux, so that a partial demagnetization of the work isobtainable in much the same manner as disclosed in my co-pendingapplication, Serial No. 371,518, filed December 24, 1940.

Referring now to Figs. 3, 4, and 5, a modified construction isillustrated wherein it is intended that only the valve piece'shall turn.The tapered arbor is similar to arbor I 0 but the cylindrical member 62is threaded to receive the plate 64, and reduced member 88 is likewisethreaded to secure the work -holding plate 58; so that the magnet "IIIand iron valve 12 are secured in position in addition to theinter-attraction of all the parts caused by the magnet.

Ji short non-magnetic sleeve! underlies'the omitted and the valve andwork holding plate 68 are of modified construction.

Valve 12 comprises an iron annulus having lands 82 similar to those at54, but instead of being free, lands 82 have non-magnetic material casttherebetween. and this material is arranged to extend out radiallybeyond the iron piece at 84 and is peripherally knurled to present ahand grip whereby the valve may be turned on sleeve I4. A series ofgrooves 88 is provided to interlock the cast metal, which may containantimony to harden it. The reason for using a non-magnetic material forthe hand grip is to prevent 'the collection of chips and sludge betweenthe plate 88 and magnet as would ocour in the absence of a gap at theperiphery of the valve.

In this modification, there is no demagnetizing flux as is occasioned byring 50 in Fig. 1,-

but in some cases it is desired to dispense with such demagnetizineffect.

' The work holding plate 68 is centrally bored and threaded to besecured to member 88, leaving a central recess 98. This plate is made upof two parts like plate 22, but in the case of the plate shown in Figs.3 and 4, both inner part 82 and outer part 94 are annular at the worksurface, having a continuous annular gap therebetween. This gap iscylindrical at portions 88, aligning with sleeve 14, but betweenportions 88, the gap extends angularly thru the plate as at I03 andforms arcs I82 at its widest extent, which align with the valve part 84.Thus, in effect, plate 88 presents spaced interfltting iron wedges tothe valve 12, but the work surface comprises a pair of spaced concentricmembers.- When lands 82 are aligned with the extending iron pieces onmember 92, the flux passes directly into member 66, but when the landsalign with the wedges integral with exterior member 94, the flux musttraverse the gap and thus pass thru any workpiece on the plate. 5

Where a magnetic holder is used for precisio work, it is essential thatthe spaced poles in the holding surface be rigidly secured against anydisplacement, and the structure be impervious to liquids used ascoolants or lubricants. To meet these requirements, it has been thepractice to fill the gaps between poles with a low-fusing expa;. .sionalloy, such as type-metal. However, none of these priorly used methodshas been found thoroughly. reliable under all circumstances. and thepresent construction overcomes this difficulty by providing an adheringmetallic bond directly between the spacing material and the ferricsurfaces facing the gap.: In the application 0f this method, reliance isplaced on the metal tin, on account of its good alloying properties.However, neither pure tin nor a mixture of tin and lead is suitable as aspacing material because of their softness.

Hardening agents, such as antimony, bismuth or arsenic maybe added toeither or both of these metals, but such admixture greatly impairs thecontact alloying properties with respect to an iron surface. 'It hasbeen found, however,

, that such-a hardened metal will readily alloy valve member I2 and analigned like sleeve I6 underlies magnet. 'I-Il. Otherwise, the end plate64 and magnet III are greatly similar to the corresponding parts in Fig.2, but the ring 50 is H relation, and the assembly heated to a degreethat at least approaches the melting point of the tin. A well heatedhardened tin alloyis then poured into the intervening spaces in whichprocess fluxes or acids may be applied to exclude oxidization.

- After solidification, such an assembly will present a structure ofgreat strength and rigidity, having metallic continuity and beingimpervious to fluids. The best results are obtained by using as afilling an alloy ofspure tin and about percent of antimony whichproduces a hard silvery metal, known in other arts as Britannia" metal.However, a considerable lead content may be added, with the object oflowering cost, although such addition will increasingly make it moredifficult to maintain the bondwith the iron.

- Applied to the present device, it will be evident that thisconstruction will produce a firmly coherent and rigid top plate 22,without dependence on looking contours or lateral pinning. Likewise, themethod may be applied in the making of the valve plate I2, where thenon-magnetic portions 04 may be cast in a mould into adhering contactwith ferric'portions '12, by the use of the above described tinning andtin alloy method.

Referring now to Fig. 6, illustrating a form of the present inventionadapted for the automatic or machine control of the valve, there isshown an annuar magnet I05, having poles on its op; posite faces, aniron base I06, and a two-part work holding plate I00, the magnet, base,and plate being, held together by any desired means such as bolts or bythe magnetic attraction of' the parts. The iron base may be screwthreaded or otherwise constructed for attachmentto a machine, and isapertured as at H0 in alignment with the aperturin the magnet. A gap II2separates the parts of the work holding plate, these parts beingconcentric. The outer part has an internal flange II4 extending belowthe inner part, and the latter is countersunk as at IIO, so that the gapII2, which follows the inner contour of the outer part divides the plateI08 at the periphery of the countersink.

A cylindrical magnetic conducting valve Ill is mounted on a rod I20 forreciprocal motion in the device. Flanges I22 center and guide the valvebesides acting as agnetic connectors,and the annular recess be canflanges provides a gap so that the valve does not contact the magnet.Suitable stops may be-utilized to restrict the reciprocatory range ofthe valve, and rod I20 may 'be actuated by any desired control mechanismto hold and release work on the work plate.

Figs. '7, 8, and 9 disclose a modification .of the construction shown inFig. 6, wherein a reverse flux circuit for total release eflect isprovided. In this instance, valve I2I is similar to valve III, but isshown mounted in a difierent manner on a rod I24, which is adapted to beused like rod I20. An iron base plate I20, which may be secured to amachine or moving 'head of any kind as by tapped holes I20, is providedwith bolts I 20 for securing the various parts together, and annularmagnet I22 is apertured as shown for passage of the bolts. However, theupper face of the magnet is grooved in a general U-shape I as at I24.

Work holding plate I is similar to plate I00,

but at spaced intervals the inner part I20 is provided with legs I40which extend to the magnet. These legs are in the shape of the areaoutlined by grooves I34 and are surrounded by sleeve-like gaps I42 whichalign with the grooves.

Hence there is a fixed direct magnetic connection between the inner workplate member I20 and the magnet, of less section than the fixedconnection between the outer work platemember and 5. the magnet.

With the valve as in Fig. 8, a small flux circuit thru the outer platepart, around the legs and.

into the valve, without traversing the gap, but the flux in the legs I40now cannot pass into the valve but must take the double loop circuitshown in broken lines, thus passing in a direction opposite to the workholding flux, in the work It should be borne in mind that without n fluxreversal, it is impossible to obtain a total release of the work, due toflux leakage, and therefore the construction shown in .Figs. 4 and 6will not fully release the work. As indicated above, it is sometimesdesired not to fully release the work, and these applications are usefulfor such purposes. However, by providinga reverse flux of smallmagnitude in work release posi- 30. tions of the valves, as in Figs. 2,8, and 9, a full release and partial demagnetization of the work isaccomplished.

1 'Theconstructions of Figs. 1-5 are adapted for manual operation of thevalves, and those of Figs. 6-9 are adapted for mechanical control,

as in automatic lathes, grinders, etc. The latter form of the inventionis also useful in transfer and pick-up devices, as the chucks can bemounted on moving heads, etc., while having 40 ti2med control devicesfor reciprocation of rods Having thus described my invention and theadvantages thereof, I do not wish to be limited to the details hereindisclosed, otherwise than as set forth in the claims, but what I claimis:

1. A permanent magnetic chuck comprising a substantially annularbi-polar magnet, a work holding plate having a plurality of radial ironmembers spaced to form gaps, and a rotatable iron element locatedbetween said magnet and plate, said element having lands adapted toselectively engage certain of said iron members and effective to directfiux from said magnet into said certain members to the substantialexclusiori of the other members, dependent upon its angular position,the opposite poles of the magnet being located axially with respectthereto.

2. A permanent magnetic chuck as recited in the preceding claimincluding a central iron support providing a return circuit for theflux, said magnet and rotatable element being mounted on the support. a

3. A permanent magnet chuck as recited in the preceding claim but oneincluding a central iron support, said magnet and rotatable elementbeing mounted on said central iron support, the latter passing axiallytherethru, and including an axial non-magnetic sleeve between saidsupport and said magnet and element.

' 4. A permanent magnet chuck comprising a pair of spaced magneticconducting members forming a work holding surface, an annular bi-polarmagnet, a fixed iron connection between one of said members and one poleof said magnet, said connection forming a support forthe chuckpan ironelement on said support, said element-being relatively rotatable withrespect to said members and providing means for selectively connectingeither of said members with the other pole of said magnet, depending onthe degree of said rotation, the opposite poles of the magnet beingarranged in a generally;

axial directionwith respect to the axis of the rotatable element.

' tion of said element, the opposite poles of the magnet forming polaraxes parallel to the axis of the rotary iron element.

6.A rotary permanent magnetic chuck comprising a pair'of spaced magneticconducting members formingv a work holding surface, said members havinginterfitting parts arranged generally radially with respect to apoint insaid either part.

surface, a bi-polar annular magnet having a fixed connection to onemember, and means effective to selectively magnetically connect theother pole of said magnet to either of said members,- said meanscomprising a rotatable iron ring having lands for selective alignmentwith the parts of either member the polar axis of said annular magnetbeing parallel to the axis of the rotatable ring. I

7. A permanent magnetic chuck as recited in the preceding claim whereinsaid iron ring is located between the magnet and work holding surfaceand is mounted for rotation relative to said members, and means securedto the ring extending to the periphery of the chuck for rotating thesame.

8. A permanent magnetic chuck comprising a pair of magnetically spacedmagnetic conducting members, said members being generally concen- .mentforming a selective connection between the other pole of said magnet andeitherbne-of said members by means of spaced radial conductors adaptedfor contact with said parts, the poles of the magnet being arranged on aline parallel to the axis of said rotary element.

9. In a magnetic chuck, the combination of a work holding platecomprising a pair of generally concentric parts, substantially radialprojections on one part, like recesses on the other part, saidprojections'extending into said recesses, and said parts being insulatedthroughout; 'with a magnetic flux source and means betweensaid sourceand plate effective to selectively pass or prevent passage of flux fromsaid source to said radial projections on either part, said meanscomprising an iron ring having lands for alignment with the radialprojections on 10. A magnetic chuck as recited in the preceding claimwherein said plate presents a flat work holding surface, and saidprojections and recesses are so arranged as to terminate short of saidsurface so as to present a circular gap conformation of said parts atsaid surface.

11. A magnetic chuck as recited in the preceding claim but one whereinsaid plate presents two opposite flat faces, said projections andrecesses being of relatively large extent on one face and extendingangularly toward the center of theplate and terminating short of theother face to form a circular conformation of said parts.

12. A permanent magnetic chuck comprising at least two magnetic membersforming a work holding plate, said members being insulated, an annularmagnet, and'a rotary magnetic element between said magnet and said plateand effective to connect a pole of said magnet to either of saidmembers, said element having a non-magnetic rim insulating said magnetfrom said plate at the periphery of said chuck, saidrim forming ahand-hold for rotating the element.

13. A magnetic holding device comprising a pair of magneticallyinsulated flux conducting members separated by magnetic insulation andforming a work holding surface, an annular bipolar magnetic flux sourcehaving a pole adjacent said members and a pole relatively remotetherefrom, an iron support for the device located within said annularmagnetic source and extending therethru and providing a direct flux pathfrom said adjacent pole thru one member to said relatively remote pole,and a rotary iron element forming means selectively eflective to causesaid support to provide a flux path to. said relatively remote pole fromthe other member and between said members, depending on the relativeposition of rotation of said element.

14. A magnetic holding device :as recited in claim 13 wherein thesupport located within the annularrmagnetic source is magneticallyinsulated from the interior surface of the latter.

15. A permanent magnet chuck comprising an annular magnet havingopposite parallel surfaces oppositely polarized, an iron element passingthrough the magnet and beyondits opposite surfaces, an iron platemagnetically connected to said element and one magnetpole at one side ofthe magnet, a plate having at least two magnetically separated parts toform a work surface at the opposite side of the magnet, one of saidparts being magnetically connected to said element, and a rotary ironplate. between the magnet and said two-part plate, said rotary platebeing effective to selectively magnetically connect either of said partswith the other magnet pole.

JOHN T. BEECHLYN.

